The longtime standard in the industry, the extruded, hollow, tapered aluminum ski pole, is rapidly being overtaken by ski poles having fiber-reinforced resin composite shafts. Fiber/resin composite shafts are lighter, stronger and more flexible than the standard aluminum ski poles. Samples of fiber/resin composite ski poles are shown in my U.S. Pat. No. 5,024,866 issued Jun. 18, 1991 and my co-pending U.S. application Ser. Nos. 826,734 filed Jan. 28, 1992; 562,317 filed Aug. 3, 1990 and 863,334 filed Apr. 2, 1992. The above patent and co-pending applications show a variety of methods and structures for achieving strong, lightweight, low-diameter, flexible ski pole shafts.
Although it is easier and less expensive to manufacture fiber/resin composite ski pole shafts in the form of straight-walled, cylindrical shafts, it is often desirable to have a finished shaft with a taper at the lower end, for both aesthetic and performance benefits. Composite pole shafts are usually formed with a hollow bore, for weight considerations and because they can be efficiently formed about some sort of mandrel. Unfortunately, prior art methods for tapering the lower end of a hollow composite ski pole shaft greatly weaken the lower end of the shaft in terms of tensile strength and resistance to crushing or breakage.
Co-pending U.S. Ser. No. 863,334 is directed in part to a fiber/resin composite ski pole shaft made from a thermosetting resin matrix and having a tapered, reinforced lower end. The inventive structure and method disclosed in that application is a marked improvement over prior art methods and apparatus for providing a tapered lower end in fiber/resin composite ski poles using thermosetting resin.
Composite ski poles made with thermosetting resin are difficult to shape or reform after the resin has set, since thermosetting resins are not capable of being resoftened by heating once hardened. In order to provide a taper in the lower end of the thermoset fiber/resin ski pole shaft, it is necessary to remove material from the outer wall at the lower end by grinding, milling or similar material-removing steps. There are two primary disadvantages inherent in such tapering operations with thermosetting poles: the grinding or milling procedure is a time-consuming and relatively expensive one; and, removal of material from the outer wall of the shaft at the lower end results in decreasing wall thickness and a correspondingly weaker shaft at the lower end.
To solve the problem created by the weakening of the lower end upon removal of the outer wall material, I invented the solution of replacing the lost wall thickness at the tapered lower end with a filler rod inserted in the hollow bore to mate therewith and internally replace the lost wall thickness. This has proven to be an effective, inexpensive, reliable structure and method for tapering the lower end in thermosetting fiber/resin composite ski poles while maintaining the strength and break-resistance of the shaft at the tapered lower end.
While the above-described structure and method of my co-pending application does not have any disadvantages, it is always desirable to find new and better ways to manufacture tapered composite ski pole shafts.